1. Field of the Invention
The present invention relates to a camera adapted to receive a flash device for flash photography, and more particularly to such camera apparatus having an automatic diaphragm control device operable for flash photography.
2. Description of the Prior Art
In co-pending U.S. patent application Ser. No. 56,938, filed on July 12, 1979, assigned to the same Assignee as the present application, there is disclosed a camera capable of being combined with a dedicated flash device which is designed to produce a preliminary flash of a relatively long duration at a substantially constant intensity prior to the production of a primary flash to be used in actual photography. The preliminary flash is produced for the purpose of providing an object with that illumination necessary for automatic diaphragm determination. The camera comprises a diaphragm aperture changeable from an initial aperture size during the duration of the preliminary flash light, means for receiving light through the diaphragm aperture during the duration of the preliminary flash to generate a first signal responsive to the intensity of the received light, and means for interrupting the change in the aperture size of the diaphragm aperture in response to the first signal to determine the aperture size.
The preliminary flash light is generally designed to be durable for a predetermined period of time sufficiently greater than the maximum time period necessary for the diaphragm aperture to be stopped-down from the fully open aperture size to the minimum aperture size thereof, e.g., 25 msec, for the purpose of determining the diaphragm aperture at any size in the changeable range thereof.
However, if the stopping-down motion of the diaphragm aperture is to be interrupted before the diaphragm is actually stopped-down to its minimum aperture size, i.e., if the diaphragm is determined at a relatively greater aperture size than the minimum aperture size such as in the case of relatively close object distance, the time necessary for the diaphragm aperture to be determined is reduced. This means that the diaphragm aperture is determined, in such a case, at a relatively early stage of the predetermined duration period of the preliminary flash light and the light energy continued to be emitted after the determination of the aperture size is an unnecessary waste.